WASHINGTON — The public should expect flight delays as furloughs kick in Sunday for air traffic controllers, although the effects may be felt unevenly from airport to airport, the head of the Federal Aviation Administration said Thursday.

Without the controller furloughs, FAA officials could find no way to cut $637 million from the agency’s budget as required by automatic, across-the-board spending cuts approved by Congress, said Michael Huerta, the agency’s administrator. The FAA has estimated there could be flight delays of about 90 minutes during peak periods.

Likewise, the agency sees no way around closing 149 air traffic control towers at small airports that are currently operated under contract for the FAA, Huerta told the Senate Appropriations Committee’s transportation subcommittee. The tower closings have been delayed until June 15.

The furloughs and tower closings were designed “to minimize impacts on the maximum number of travelers,” he said. But he acknowledged, “We’re forced to choose between very unattractive options.”

A key Republican lawmaker accused the White House of deliberately trying to upset the public.

“They want to cause the most pain to the American people out there so they will put pressure on Congress to back away from sequestration (spending cuts),” Rep. Bill Shuster of Pennsylvania told a transportation gathering hosted by the National Journal news magazine. Shuster chairs the House Transportation and Infrastructure Committee.

“I believe he (President Barack Obama) is instructing his agencies to do things that inflict the most pain on the most people. This should be laid right at the president’s feet,” Shuster said.

The FAA’s 47,000 employees — including nearly 15,000 controllers — are scheduled for one furlough day every other week through Sept. 30. That will reduce the number of controller hours on duty and pay by 10 percent, Huerta said.

In order to maintain safety with fewer controllers, takeoffs and landings will have to be less frequent, and planes will have to be spaced farther apart when they are in the air, he said. That reduces the efficiency of the air traffic system, creating delays, he said.

The impacts may differ depending upon the airport, Huerta said. At Chicago’s busy O’Hare International Airport, for example, it’s possible there won’t be a full complement of controllers to staff the airport’s two control towers, requiring one tower to be shutdown.

Without a second tower, one of the airport’s runways will have to shut down, reducing takeoffs and landings, he said.

Most airports only operate one control tower.

The employee furloughs will save an estimated $200 million, and the tower closings will save $25 million, Huerta said.

A spokesman for the union that represents air traffic controllers said the ramifications of the furloughs are still unclear.

“We don’t know with any specificity what’s going to happen until this goes down,” Doug Church of the National Air Traffic Controllers Association said. “It is not a good thing for aviation to take away staffing at any level.”

But air travelers may get a break on the ground. A senior Transportation Security Administration official said Thursday he doesn’t expect furloughs for his agency, which staffs airport security across the nation. And, he said, longer wait times at checkpoints have not yet materialized as a result of so-called sequestration, as Homeland Security Secretary Janet Napolitano warned last month.

Congress included additional money for security officers in a budget bill for the remainder of the 2013 fiscal year, and long wait times have been averted for now, TSA Deputy Administrator John Halinski told a congressional panel. Obama signed the budget bill last month.

Halinski cautioned that even with the extra funding, travelers may see lines and wait times increase during busy travel periods.